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Insights and Best Practices to significantly improve email deliverability

Do your clients complain about not receiving your emails or newsletters? Do most of your emails end up in spam folders? If this sounds familiar, you’re not alone.

Do you know how many emails are sent every day?
Let’s answer that question differently. Over 100 billion emails get flagged as spam every day! This number is nearly 50% of the total daily email traffic, currently at a staggering 270 billion! Although this seems to be good news for recipients, senders are a harrowed lot. Over 17% of emails sent by legitimate senders around the world failed to reach their inbox. The global inbox placement rate also saw a decline from 85% to 83%. To put this into pure numbers, for every six legitimate emails sent commercially, only 5 make it through.

Why are emails so important?

Ever since emails transitioned from ARPANET’s systems and led to the email boom in 1995, the popularity of emails as our primary source of correspondence, industry insights, news and reviews has only seen an uptick. Emails have reduced truckloads of paper that would otherwise be wasted in printed memos and have helped people communicate instantly, making inland and aerogramme letters obsolete.

Today, people send millions of emails every minute, making it one of the most-used services on the internet. From personal emails to office correspondence, marketing campaigns, newsletters and information broadcasts—emails are the mainstay of communication for every industry worldwide.

What are the factors that determine the failure or success of email deliverability?

To understand this better, let us first understand the goal of email deliverability. The purpose of email deliverability is to get your email to your recipient’s inbox. Although an email that ends up in the spam or junk folders is marked delivered, it is of no use as no one will read it unless you explicitly ask them to remove the email from their junk folder.

Who is involved in the email deliverability process?

The process of email delivery is simple. Here’s how it works:
A. You compose and send an email
B. Your email is checked by the mail transfer agent system
C. Your email is forwarded to the recipient’s mail transfer agent system
D. Your email is forwarded to the email client used by your intended recipient
E. Checks are applied by the end user’s email client for individual preferences
F. Your email is delivered to your intended recipient

Although this sounds simple, email delivery depends on tasks performed by entities and services in the email sending, forwarding and delivering process.

Email deliverability depends on four distinct entities: email senders, the sending gateway, the receiving gateway and the actual recipient.

1. Email senders

An email sender is a person, entity or software program that sends an email to you. Email senders are divided into two distinct subcategories:

Legitimate or authenticated senders

Legitimate senders include individuals who are authorized to send you emails such as individuals and campaigners that you opt into. These can be classified into three subcategories:

A. Legitimate email senders – these include individuals sending you emails through Mail User Agents (also known as email programs, email software or MUA). These emails are typically sent through a web browser using webmail (Gmail, Yahoo Mail, Outlook, Zoho) or email clients such as Outlook, Mozilla Thunderbird and Mail (on Apple devices).

B. Automated mail sending systems – Often, banks, hospitals and other agencies may send email notifications to you on events or actions performed by you. A good example is getting an email every time you purchase something online or transfer funds into someone’s account.

C. Marketing campaigners – This group includes opt-in email campaigns that you subscribed to, such as our amazing newsletter!


Spammers are individuals and automated programs that send you malicious emails that may contain viruses, worms, set off phishing attacks and may compromise your organization’s network.

A. Individual Spammers – Individuals sending you emails with malicious intents, such as phishing, identity theft or information theft. Typical examples include the Nigerian lottery scams, appeals for help from unknown people asking for your banking information and more.

B. Spambots – This list includes automated software sending mail from systems infected by viruses and worms, or other compromised systems that the attackers have access to.

2. Email sending gateways or Mail Transfer Agents (MTAs)

Email ending gateways or mail transfer agents are automated systems, services and entities that analyze and send emails on your behalf. When you click the Send button after composing an email, these systems check your email for spammy content, security and perform other policy-driven checks before actually sending your email to the receiving gateway.

Examples of sending gateways include Gmail,, Yahoo Mail, your email or web hosting provider such as Pack Web Hosting or your ISP.

Email sending gateways perform the following tasks:

  • Applying an outgoing email policy check to your emails before they are sent
  • Checking the IP address reputation of the sender
  • Forwarding the email to the recipient email gateway or MTA.

3. Receiving gateways or MTAs of the recipient

In addition to checks at your end by your MTA, similar security checks and processes are also performed by the mail transfer agent systems at your recipient’s end. Your emails will be checked for spammy content and security risks. If your recipient is in a large organization, your emails are then routed to the organization’s own security systems for analysis and checks according to their internal organizational policies.

These policies also take into account the recipient’s preferences, emails flagged as spam by them, and their general behaviour towards handling emails.

4. Actual recipients

Finally, if all goes well, your email will reach your intended recipient after this long and arduous journey. Note that your email may also be subject to checks and routing at the client used by the recipient, especially if they are using clients such as Outlook and Mozilla.

Although all of this may seem to just take a second or two, your email undergoes a long journey of checks, validations and confirmations before it reaches its intended recipient.

Examining the factors that determine the success or failure of email deliverability

Imagine this scenario: You have just been informed that you missed a project submission deadline or an important business opportunity. Your email failed to reach the intended recipient, and as a result, you have missed out on something big.

This may happen to anyone – and sometimes due to no fault of their own. Here’s what you can do next to ensure that your emails, newsletters and all other communications get delivered to your customer’s inboxes without hiccups:

  • Check for invalid email addresses
    Invalid email addresses indicate to ISPs that you purchased a harvested list of emails, categorizing you as a spammer. Ensure that you periodically clean your email list.
  • Remove spam trap addresses
    Anti-spam entities and ISPs set up spam trap email addresses to identify and block spammers. These spam trap email addresses are often posted on websites so spammers can harvest them, and ISPs can block them effectively.
  • Reduce complaints
    If a user clicks “This is spam” or “Report as spam”, your sending addresses will be flagged as spam by the ISP or blacklisting organization, making email delivery difficult. You can also ensure that you only send emails to opt-in recipients. Additionally, making the unsubscribe link visible and processing records on time 
  • Proper sending infrastructure
    It would help if you always chose a reliable email provider with a high IP reputation and proper authentication (SPF, DKIM and rDNS records). Many recipients see poor infrastructure as an indication of spam. Additionally, send emails from an actual email address that reflects your brand. If you use your SMTP server with a custom email system, ensure that you implement valid email authentication using PTR, DKIM and RDNS records. 
  • Domain and IP reputation
    Every ISP will give you a domain and IP score, which your reputation. If you have a shared IP, your reputation can be affected by other senders using the same IP. Understand that if you use the same domain for marketing and transactional emails, negative feedback for marketing emails will also impact transactional emails’ deliverability. Using different subdomains to separate your transactional and marketing emails can also be very helpful. This solution will also help you to protect your primary domain. Additionally, using feedback loops or FBLs are an excellent source to know who dislikes your emails and improve mailing practices.
  • Email authentication
    Using protocols that prove the authenticity of the source of your emails is essential. Protocols such as SPF, DKIM and DMARC confirm that you sent the email in question and no one altered it. Ensuring the same IP address and “from” email address enhances credibility
  • Spam Rate
    A healthy spam rate means that no more than 0.1% of your emails should end up in spam folders. You can check your email spam score by using tools such as MailTester, GlockTools and many others. A good subject line, reducing spam-filter trigger words and ensuring quality content can reduce spam rates.
  • Content
    Spammy content impacts the deliverability of your email. Avoid broken HTML code, small text vs image ratios and links from blacklisted domains.
  • End-user engagement
    Email Service Providers like Gmail or Yahoo, monitor end-user engagement to decide if users are facing spam. Checking if users mark your email as spam, delete it or add you to the white-list are actions that ISPs monitor to train their spam engines.

Avoid this to improve delivery outcome

  • Harvesting email addresses or buying email lists
  • Sending emails to those who did not opt-in
  • Sending emails to inactive email addresses
  • Sending emails to group email IDs
  • Sending emails with spammy content

Do this to improve delivery outcomes

  • Sign up with Google Postmaster, Yahoo Feedback and Microsoft SDNS
  • Have a great email sign-up process
  • Check your spam scores
  • Maintain a proper (60:40) text-image ratio
  • Reduce email size (an email of 100kb is ideal)
  • Personalize content to reduce spam incidents

Although this is not an exhaustive list of reasons and tips, the deliverability of emails also depends on dozens of other technical reasons. Additionally, these steps will also help you send more relevant emails that drive engagement, making it a win-win situation for everyone.

If you continue to face issues even after following all our best practices, it would be an excellent time to send a message to the email experts at Pack Web Hosting. With years of experience and an outstanding technical team, Pack Web Hosting’s services and solutions will help you ensure deliverability and drive customer engagement.